Method of metal bending



July 14, 1942. B. WELSER ETAL 0,

METHODQOF METAL BENDING Filed April 21, 1938 grwe/wm I6 ,Brin/tou/ nbseran Maurice G. Jewett,

I Gum/M446 Patented July 14, 1942 i METHOD OF METAL BENDING Brinton Welser and Maurice G. Jewett, Milwaukee, Wis., assignors to Chain Belt Company, Milwaukee, Wis., a corporation of Wisconsin Application April 21, 1938, Serial No. 203,430

2 Claims.

The invention relates to a method of bending metal, and has for one of its principal objects an improvement over the prior methods of bending metal elements in the cold whereby the stresses normally set up in the fibers of the metal during the bending operation may be substantially relieved, and the cross sectional area and contour of the element preserved.

While in its broadest aspect the invention is by no means limited thereto, for purposes of disclosure it has been illustrated and will be described in its application to the securing of solid metal cotters in the pintles of power transmitting sprocket chains, a field in which it has already received extensive field tests and shown a marked degree of success in overcoming certain defects present in the methods heretofore employed in securing such cotters against unintentional displacement.

In a well known form of such chains the pintles which connect the links are provided at one end with an enlarged head which engages one of the link side bars to limit axial movement of the pintle in one direction. The other end of the pintle is unheaded, and is provided adjacent the outer face of the opposite side bar with a transverse aperture, into which is introduced a locking pin or cotter which co-operates with the last mentioned side bar to prevent axial movement of the pintle in the other direction, whereby it might be unintentionally displaced.

In high speed chains it has been found almost essential to use solid cotter pins-to secure a tight fit, since it has thus far been found impossible to secure the well known split cotters tightly l enough to overcome excessive vibration, with resultant rapid wear and a high percentage of breakage. The tight fitting solid cotters, which in many cases are pressed or driven into the pintle apertures to secure intimate contact and thereby eliminate wear due to vibration, may be provided at one end with a preformed head, with the other end which projects beyond the pintle being deformed in various Ways after insertion to prevent the cotter from being easily displaced.

One method of securing the solid cotters, which is perhaps the easiest to accomplish and therefore extensively used, is to merely bend the said end in a plane substantially parallel to the side bar face. This is ordinarily done by hammering or otherwise applying force at substantially right angles to the cotter axis until the bend is accomplished.

Actual experience has demonstrated-however, that in this type of bending the metal is unduly distorted at the bend, with the metal on the inside, the radius of Which is of necessity small, being excessively compressed or actually ruptured, and therefore weakened, while that on the outside is excessively stretched, thereby reducing the cross sectional area and area in contact with the chain pintle. As a result, it is not uncommon for solid cotters so secured to break off at the bend, and then work out, permitting the pintle in turn to work out, and the chain to fly apart, which may be extremelydisastrous at high speed.

To prevent undue distortion of the fiber of the metal the practice of deforming the solid cotter pin after heating to a red heat is often adopted, but such heating will cause'the cotter pin to expand in the aperture, and since the pin will shrink when again cold, it 'will not then fill the aperture as intimately as a cotter pin which has been bent cold. In fact, solid cotters deformed while hot, are still subject to excessive vibration, with resultant wear and substantial percentage of breakage.

In a more limited aspect, it is therefore a further object of the present invention to overcome the above defects, and to provide a method of securing solid cotter pins of this and similar character which can be quickly and cheaply carried out, and at the same time substantially eliminate breakage in service and undesired displacement of the cotters.

It is a further object of the'inventionto provide a securement which, while effectively retaining the cotters against unintentional displacement, will nevertheless permit of their being quickly and easily removed in the field Whenever it may be necessary to dismantle the elements for repairs or displacements.

With the above and other objects in view the invention consists in the novel steps and combinations of steps constituting the method of i metal bending, and in the novel product thereof, all as more fully hereinafter described and particularly pointed out inthe app-ended claims.

Referring to the accompanying drawing forming a part of this specification, which illustrates one way of performing thebending, and in which like reference characters designate like parts in all the views:

Figure l is a plan view, more or less diagrammatic, of a portion of a high speed power transmission chain of the type referred to above, fitted with solid pintle retaining cotters of a kind adapted for a typical carrying out of thepresent invention;

Fig. 2 is-a side elevational View of the chain shown in Fig. 1, illustrating the initial step in the present process of bending the cotters;

Fig. 3 is an enlarged diagrammatic sectional elevational view of the end of the chain pintle and cotter, illustrating a position of the elements intermediate the initial and final operations;

Fig. 4 is a view similar to Fig. 3, but illustrating the elements at the conclusion of the operation;

Fig. 5 is a view similar to Fig. 4, but illustrating the effect of bending a cotter by force applied at substantially right angles to its axis, as for example by hammer blows, in accordance with the method heretofore employed; and

Figs. 6, '7 and 8 are enlarged cross sectional views taken on the lines 6B, 'II, and 8-8 of Figs. 3, 4 and 5 respectively, showing the cross sectional areas and contours of the cotters in the respective stages illustrated in said last mentioned figures.

The chain shown in the said drawing comprises a plurality of links II] composed of spaced side bars II and I2 which are pivotally connected by the chain pintles I3. The said pintles are each provided at one end with an enlarged head 14 to limit axial movement in one direction, and at the other end project beyond the outer face of side bars I2, substantially as shown in Figure 1. This projecting portion is provided with a transverse aperture I5 adjacent the said outer face of side bar I2 for the reception of the locking pin or cotter I6. The said cotter is preferably provided with a pre-formed head I! on one end, while the opposite end I8 projects beyond the pintle surface as will be readily understood.

As above explained, the projecting end portion I8 of the cotter is usually deformed in some manner in order to retain the pin in place. In some instances the deformation has been accomplished by swaging a head upon this end of the pin, while in others the projecting end has been merely bent in a plane either parallel to or at right angles to the face of the side bar I2. However, as above set forth, such bending as heretofore carried out excessively distorts the metal of the pin, unduly stretching that On the outside of the bend thereby reducing the cross-sectional area so that the cotter fills the hole in the chain pintle less completely, and, if excessive, compressing that portion on the inner side of the bend to such an extent as to crush it and render it liable to breakage at the bend under the rigorous conditions of high speed operation.

In accordance with the present invention the projecting end portions I8 of the cotter I6 are secured in the following manner, which actual tests in the field have shown to materially reduce breakage of the pins at the bend. In this method the chain is positioned on a surface which may be the bed of a suitable press and which is provided with a block or anvil 2| having a surface 23 which is inclined at an angle of say approximately to the vertical axis of the cotter. The cotter is positioned substantially as shown in Figure 2 with its lower corner in contact with the upper portion of the surface 23 whereupon a pressure member 25 is caused to exert longitudinal pressure upon the head II of the cotter, as indicated by the arrow A in Figs. 3 and 4, forcing the lower portion I 8 to frictionally traverse the said surface 23. It will be understood that during the application of this longitudinal pressure the chain links are held against longitudinal movement, and since the chain pintle is held against rotation in the side bars II and I2 by a flat I3, a bending of the projecting end portion I8 of cotter I8 toward the left, as viewed in Fig. 2, is accomplished.

This bending of course produces some compression of the fibers of the metal on the inside of the bend, and some stretching and tensioning of the fibers on the outside of the bend, with a consequent change in the cross sectional contour and reduction in the cross sectional area at the bend. By the time the elements have reached the intermediate position shown in Fig. 3in which the bend is substantially completed, and the chain pintle I3 has only the distance represented by the space between the lines a and b to travel to complete the operationthe outside of the bend has been somewhat drawn away from the lower portion of the wall of the pintle aperture I5, as indicated at 26 in said Fig. 3, and the cross sectional area of the cotter at the bend somewhat reduced and its contour changed to a more or less elliptical shape, as indicated in Fig. 6, wherein the broken line indicates the normal circular contour of the cotter.

However, due to the frictional engagement of the cotter with the surface 23 as it is forced along the latter, the stretching of the fibers in the bend and consequent change of area and shape is not as pronounced as in the case where the bend is accomplished by force applied, as by hammer blows, at substantially right angles to the cotter axis. The effect of such method of bending is illustrated in Fig. 5, wherein the stretching of the fibers on the outside of the bend, as a result of force applied to the projecting end I8 of the cotter as indicated by the arrow B, has drawn more of the cotter surface out of contact with the wall of pintle aperture I5, as indicated at 21. The cross sectional area has also been reduced to a greater extent, and the contour made more elliptical, as shown in Fig. 8.

Referring again to Fig. 3, while as above stated the frictional traverse of the cotter over the surface 23 has appreciably reduced the stretching of the metal of the cotter, and its consequent change of area and contour, nevertheless some such changes have taken place, and the metal fibers on the outside of the bend are tensioned to some extent. In many cases, and particularly in the present illustrative example of a sprocket chain intended for use at high speeds, i. e. up to say 3,000 ft. per min., changes in the cotters even to this extent may be instrumental in causing breakage or-failures of the cotters, with disastrous results at such speeds. That is to say, although the cotters may be a press or drive fit in the pintle apertures when initially inserted, the reduction in area due to bending is sufficient to destroy such fit to such an extent as to permit them to vibrate or chatter at high speeds, which vibration, due to the distorted condition of the metal fibers, results in a relatively high percentage of cotter failures.

To overcome this, the present invention relieves the tension on the metal fibers and restores the cotters to their normal cross sectional area and contour, thereby causing them to tightly and intimately contact the walls of the pintle apertures, just as they did before bending. This is accomplished by continuing the movement of the pintle and cotter from the position shown in Fig. 3 to that shown in Fig. 4, thereby bringing the end of the cotter into pressural engagement with the flat surface 24 of the block or anvil 2|. This engagement has the effect of pushing longitudinally upwardly on the metal on the outside of the bend, thus relieving the tension on the fibers and restoring the area and contour of the cotter at the bend, as indicated in Figs. 4 and '7, thus causing it to again intimately contact the walls of the pintle aperture throughout their length. As a result, the cotters will be tightly held aga nst vibration or chattering, and with all tension substantially completely relieved; and field observations have shown a material reduction in the percentage of breakage in cotters secured in this manner.

The pressural engagement of the cotter end with the surface 2d is such as to accomplish a relief of the tension and a restoration of the contour and area at the bend Without a general heading effect on the projecting end l8 of the cotter, and as a result the latter may be removed in case of necessity Without the use of any special tools, since the deflected end portion may be bent back to alinement with the body, as by hammer blows, and then driven out of the pintle aperture with a hammer or a drift,

While the invention is particularly applicable to the securement of cotters in high speed chains, in which field it has already received extensive use, it will be readily apparent that it may also find use in numerous other fields wherein it is desired to employ metal elements bent in the cold, in which the initial cross sectional area and contour is preserved and tension of the bend is substantially eliminated; and it is obvious that those skilled in the art may vary the precise steps above recited without departing from the spirit of the invention, in View of which it is not wished to be limited to the above disclosure, except as may be required by the appended claims.

What is claimed is:

1. The method of bending metallic elements, which comprises causing the element to traverse a fixed surface disposed at an angle to the path of travel of the element While restraining a portion of the element against tranverse displacement, said traverse producing a lateral deflection of another portion of the element while partially restraining stretching and tensioning of the fibers of the metal on the outside of the bend through frictional resistance; and then causing said element to engage another fixed surface arranged to offer resistance longitudinally of the element to substantially relieve such tension as has been produced.

2. The method of securing solid metallic cottons in the apertures of other elements, which comprises inserting a tightly fitting cotter into such aperture with a portion of the cotter projecting beyond the element; moving the element and cotter longitudinally of the latter while restraining the element against transverse movement, the projecting end of said cotter being in frictional engagement with a fixed surface inclined to the path of movement of the cotter, whereby the projecting portion of said cotter is laterally deflected, said frictional engagement serving to partially restrain stretching and tensioning of the metal fibers on the outside of the bend and consequent change in the cross sectional area and contour of the cotter which tends to loosen it in the aperture; and causing the end of the cotter to engage another fixed surface arranged to exert force longitudinally of the cotter to relieve such tension as has been produced and restore the cross sectional area and contour of the cotter whereby the latter will intimately contact the walls of element aperture throughout their length at the conclusion of the bending operation.

BRINTON WELSER. MAURICE G. JEWETT. 

